Switching circuitry for sequential fuel injection

ABSTRACT

SWITCHING CIRCUITRY FOR SEQUENTIAL FUEL INJECTION IN WHICH TRANSISTOR DRIVER STAGES FOR INJECTOR VALVE ACTUATORS ARE COUPLED TO AND GATE MEANS HAVING INPUTS TO WHICH TIMING SIGNALS ARE APPLIED FROM FLIP-FLOP MEANS AND HAVING ADDITIONAL INPUTS TO WHICH CONTROL SIGNALS ARE APPLIED FROM A SEQUENCING CIRCUIT, PREFERABLY COMPRISING A DIGITAL COUNTER AND DECODER GATES FOR DEVELOPING THE CONTROL SIGNALS. THE CONTROL SIGNALS HAVE A DURATION SUFFICIENT TO ALLOW THE TIMING SIGNALS TO EFFECT OPENING OF THE INJECTOR VALVES FOR NEARLY 180 DEGREES OF CRANKSHAFT ROTATION, IN TIMED RELATION TO THE INTAKE STROKES. IN ONE EMBODIMENT, DESIGNED FOR A FOUR CYLINDER ENGINE, A SINGLE TIMING FLIPFLOP IS USED WHILE IN OTHER EMBODIMENTS, DESIGNED FOR EIGHT CYLINDER ENGINES, TWO FLIP-FLOPS ARE USED IN A MANNER TO PERMIT OVERLAP OF THE TIMES OF OPENING OF THE FUEL INJECTION VALVES. ADDITIONAL FEATURES RELATE TO THE APPLICATION OF PRE AND POST BIAS SIGNALS IN COMBINATION WITH A SHORT DURATION VALVE OPENING PULSE IN A MANNER TO PERMIT RAPID AND ACCURATE CONTROL OF THE OPENING AND CLOSING OF THE INJECTOR VALVES.

United States Patent [191 Scot'ield June 28, 1974 SWITCHING CIRCUITRYFOR SEQUENTIAL FUEL INJECTION [75] Inventor: Bruce A. Scofield, FortWayne, Ind.

[73] Assignee: International Harvester Company,

Chicago, Ill.

[22] Filed: June 21, 1972 [21] Appl. No.: 265,047

[52] US. Cl. 123/32 EA, 317/123, 123/119, 123/139 AW, 123/140 MC [51]Int. Cl. F02m 51/06 [58] Field of Search 123/32 EA, 119 R [56]References Cited UNITED STATES PATENTS 2,815,009 12/1957 Pribble 123/32EA 3,612,009 10/1971 Kamazuka et al 123/32 EA 3,612,011 10/1971MonpetiLf. 123/32 EA 3,621,826 ll/1971 Chrestensen 123/148 E PrimaryExaminerLaurence M. Goodridge Attorney, Agent, or FirmFrederick J.Krubel; Floyd B. Harman [57 ABSTRACT Switching circuitry for sequentialfuel injection in which transistor driver stages for injector valveactuators are coupled to AND gate means having inputs to which timingsignals are applied from flip-flop means and having additional inputs towhich control signals are applied from a sequencing circuit, preferablycomprising a digital counter and decoder gates for developing thecontrol signals. The control signals have a duration sufficient to allowthe timing signals to effect opening of the injector valves for nearly180 degrees of crankshaft rotation, in timed relation to the intakestrokes. In one embodiment, designed for a four cylinder engine, asingle timing flip-flop is used while in other embodiments, designed foreight cylinder engines, two flip-flops are used in a manner to permitoverlap of the times of opening of the fuel injection valves. Additionalfeatures relate to the application of pre and post bias signals incombination with a short duration valve opening pulse in a manner topermit rapid and accurate control of the opening and closing of theinjector valves.

17 Claims 11 Drawing Figures COMPUTER TIMER SEQUENCE 38W CIRCUIT *25 I i1 l 1 AIR 1 DRIVER 324 J IEMP CIRCUIT IO\, 11111 F UEL TANK PATENTED H m3820.198

SHEET 1 OF 9 FIG 3 3 i 89 COMPUTER TIMER 1 SEQUENCE 38 CIRCUIT *25 I l II AIR i DRIVER J24 TEMP CIRCUIT /O\ 35 1/1/1111 FUEL TANK FIG 2 2-B/T f[30 COUNTER 53 l I l I 129 DECODER -52 54 I Q55 DELAY FLIP MV FLOP 4a 4950 5/ AND D w AND ;Q, V08 47 DR L07? L13)? LDR 45 57 SHKU 2 (IF 9PATENTEDJUH28 I974 MTENTEI] JUN 2 8 I974 SHEET 3 BF 9 PATENTEDJUII28I974 SHEET 9, [IF 9 I I I I I I I f'llll'lulllllllllIlII-lllllll 1SWITCHING CIRCUITRY FOR SEQUENTIAL FUEL INJECTION This invention relatesto switching circuitry for sequential fuel injection control and moreparticularly to circuitry which is highly efficient and reliable inoperation and which permits very accurate control of the timing ofopening and closing of sequentially operated fuel injector valves andthereby highly accurate control of the amounts of fuel injected.

BACKGROUND OF THE INVENTION Sequential fuel injection systems haveheretofore been proposed using one solenoid operated valve for eachcylinder to allow flow of a controlled amount of fuel during each intakestroke, with the amount of fuel being controlled by controlling theduration of electrical pulses applied through a distributor or the likeused to allocate the application of the pulses to the valves inaccordance with the firing order of the engine. Such distributors havenot been entirely satisfactory and reli able in operation. For example,with a distributor in which a rotating contact has sliding engagementwith commutator segments, there are problems with arcing, high contactresistance and wear, interfering with proper performance andnecessitating frequent servicmg.

SUMMARY OF THE INVENTION This invention was evolved with the generalobject of overcoming the disadvantages of prior art systems and ofproviding a system permitting highly efficient, accurate and reliablecontrol of the application of control signals to injector valveactuators.

A more specific object of the invention is to provide sequencingcircuitry using solid state devices and integrated circuits for maximumreliability coupled with low cost.

Another object of the invention is to provide a system permittingsequential operation of injector valves and permitting opening of thevalves through substantially 180 degrees of crankshaft rotation.

A further object of the invention is to provide a sys tem permittingcontrol of operating current for rapid and accurate opening and closingof injector valves.

The systems of this invention may be used, for example, in controllinginjection of fuel in an internal combustion engine provided with asolenoid-operated injector valve for each cylinder. The injector valvesmay be coupled to a header in which the fuel may be maintained at asubstantially constant pressure and each injector valve may, forexample, be arranged to inject fuel into the intake manifold just aheadof the intake valve for the associated cylinder. By controlling theduration of the time interval in which each injector valve is opened,the amount of fuel supplied is thereby controlled.

In accordance with this invention, the injector valve actuators arecoupled to AND gates having first inputs to which timing signals areapplied from flip-flop means and having second inputs to which controlsignals are applied from a sequencing circuit. Each control signal mayhave a duration of approximately 180 degrees of crankshaft rotation,synchronized with the opening of the intake valve, and each timingsignal may have a duration variable from a relatively small angle to anangle approaching 180 degrees, to pennit a wide variation in the amountof fuel supplied during each cycle.

The sequencing means preferably comprises a plurality of flip-flopsforming a digital counter arranged to count a predetermined number ofpulses equal to the number of cylinders and decoder gate means coupledto the flip-flopsfor developing the sequencing signals.

In a system designed for a four cylinder engine, the digital counter mayhave two flip-flops while the timer flip-flop means may comprise asingle flip-flop arranged to develop a single series of timing signalswhich are applied to the first inputs of all of the gate means. In asystem designed for an eight cylinder engine, the flip-flop meanscomprises first and second flip-flops arranged to develop first andsecond series of timing signals in phase displaced relation, one seriesbeing applied to the second inputs of one group of four gates and theother series being applied to the second inputs of a second group offour gates. The beginnings of the timing signals of the first series maybe displaced degrees crankshaft rotation from the beginnings of thesecond series of timing signals. With the two flip-flops and thedivision of the gates into two groups, the times of openings of theinjector valve means can overlap and each valve can be opened for uptodegrees of crankshaft rotation.

The two flip-flops may be controlled by two timers, using twoalternative circuit arrangements. In one arrangement, the two timers aretriggered alternately by signals in 90 degree phase relation and eachtimer controls one of the flip-flops. In another arrangement, the timersare connected in cascade with a first timer being triggered by pulseshaving a 90 degree phase difference from one pulse to the next and thesecond timer is triggered from the first timer, with a third flip-flopbeing used for alternately controlling the two flip-flops from thesecond timer.

Additional important features of the invention relate to the applicationof pre and post bias signals in combination with a short duration valveopening pulse in a manner such as to permit rapid and accurate controlof the times of opening and closing of the injector valves.

This invention contemplates other objects, features and advantages whichwill become more fully apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings. BREIF DE- SCRIPTION OF THE DRAWINGS FIG. I is a schematic diagram of a sequential fuelinjection system for a four cylinder engine, incorporating switchingcircuitry according to the invention;

FIG. 2 is a block diagram of sequence and driver circuits of the systemof FIG. 1;

FIG. 3 is a circuit diagram of counter, decoder, gating and drivercircuitry shown in block form in FIG. 2;

FIG. 4 is a wave form diagram for explanation of the circuitry of FIGS.2 and 3;

FIG. 5 is a schematic diagram of one preferred form of switchingcircuitry for an eight cylinder engine;

FIG. 6 is a wave form diagram for explanation of the operation of thecircuitry of FIG. 5;

FIG. 7 is a schematic diagram of another preferred form of systemdesigned for an eight cylinder engine;

FIG. 8 is a schematic diagram of a third form of system designed for aneight cylinder engine;

FIG. 9 is a wave form diagram for explanation of the operation of thesystems of FIGS. 7 and 8;

FIG. 10 is a circuit diagram of a driver stage used in the systems ofFIGS. 5, 7 and 8; and

FIG. 11 is a circuit diagram of an electronic switch and a monostablemultivibrator used in the system of FIG. 8.

Reference numeral 10 generally designates a sequential fuel injectionsystem designed for a four cylinder engine, incorporating switchingcircuitry constructed in accordance with the principles of theinvention. An individual solenoid-operated injection nozzle or valve isprovided for each cylinder of an engine and each valve is opened onceduring every revolution of the engine cam shaft, or once during everyother revolution of the drive shaft, in the case of a four cycle engine.In the system 10, designed for a four-cylinder engine, there are fourinjection valves, 11-14, FIG. 2, which may be mounted on an intakemanifold 15 of an engine 16 in the manner as shown diagrammatically inFIG. 1. As also shown in FIG. 1, the injection valves are connected to aheader 18 which is connected through a filter 19 to the outlet of a pump20 having an inlet connected to a fuel tank 21. A pressure regulator 22is provided between the header 18 in the fuel tank 21 to maintain thepressure in the header at a substantially constant valve which may be onthe order of 40 PSIG, by way of example.

The injection valves 11-14 are connected to a driver circuit 24controlled from a sequence circuit 25. The sequence circuit 25 receivescontrol and triggering signals from a distributor 26 and an ignitioncoil 27 of the engine and controls the time intervals in which thevalves 11-14 may be energized, to synchronize the injection of fuel inrelation to the intake strokes of the respective cylinders. The sequencecircuit 25 is also connected through lines 29 and 30 to a timer 31 whichis controlled from a computer 32.

Computer 32 controls the timer 31 and through the sequenceand drivercircuits 25 and 24 the time duration of each opening of each injectionvalve is controlled, the control being a function of the prevailingoperating conditions at the time of injection. In the illustratedarrangement, the computer 32 receives pulses from the ignition coil 27to develop a speed signal and is connected to switches 33 and 34 mountedon a throttle 35 of the engine 16, switch 33 being operated when thethrottle is closed and switch 34 being operated which the throttle inwide open. Computer 32 is also connected to a sensor 36 which sensesintake manifold absolute pressure, to a sensor 37 which senses coolanttemperature and to a sensor 38 which senses air temperature, asdiagrammatically illustrated. The computer 32 may also contain circuitryfor sensing acceleration and also the rate of change of intake manifoldabsolute pressure. In response to such sensed operating conditions, thecomputer 32 may develop an analog voltage output which controls theduration of a pulse generated by timer 3] and applied to the sequencecircuit through line 29, the beginning of each pulse being determined bya triggering signal applied through line 30. It should be understoodthat the timer 31 and computer 32 are not, by themselves, part of thepresent invention, and, so far as concerns the switching circuitry ofthis invention, any suitable means could be employed to generate atiming signal or pulse of controllable duration. By way of example, theduration of the timing signal or pulse may typically be on the order offrom 2 and 12 milliseconds.

Referring now to FIG. 2, the solenoids of the injection valves 11-14 areconnected between ground and outputs of four driver stages 41-44connected to a power supply terminal 45 to which battery voltage of onthe order or twelve volts may be supplied. Inputs of the driver stages41-44 are connected to the outputs of four AND gates 47-50 having inputsconnected to gether into the output of a flip-flop 51 and havingadditional inputs connected through a decoder 52 to outputs of a tw0-bitcounter 53. Inputs of the flip-flop 51 and of the counter 53 areconnected to the output of a delay monostable multivibrator 54 having aninput connected through a line 55 to the ignition coil 27. An additionalinput of the counter 53 is connected to the output of a secondmonostable delay multivibrator 56 having an input connected through aline 57 to the distributor 26.

In the general operation of the system, signals responsive to ignitionpulses are applied through the delay multivibrator 54 to the counter 53to advance the count thereof and also to the flip-flop 51 which is thenplaced in a set condition, a signal being then applied through line 30to the timer 31 to initiate operation thereof. Timer 31 then generates apulse of controlled length at the termination of which a signal on line29 resets the flip-flop 51. When the flip-flop 51 is set, a signal isapplied through one of the AND gates 47-50, depending upon the conditionof the counter 52, .to one of the driver stages 41-44, to energize oneof the injection valves 11-14 for a time interval corresponding to thetiming pulse applied from the timer 31. The signal applied from thedistributor 26 through the delay multivibrator 56 to the counter 53 isfor the purpose of correlating the operation of the counter 53 to thefiring sequence of the engine.

Referring to FIG. 3, the driver stages 41-44 include power transistors61-64 having emitters connected to the injection valves 11-14 and havingcollectors connected through resistors 65-68 to the power supplyterminal 45. The bases of the transistors 61-64 are connected throughresistors 69-72 to the power supply terminal 45 and to the collectors oftransistors 73-76 the emitters of which are connected to ground and thebases of which are connected through resistors 77-80 to a line 81 whichis connected through a resistor 82 to ground and which is also connectedto an emitter of a transistor 83 the collector of which is connected tothe power supply terminal 45 and the base of which is connected througha resistor 84 to the output of the flipflop 51. The bases of thetransistors 61-64 are additionally connected to the collectors oftransistors 85-88 and also to the collectors of transistors 89-92.

The bases of transistors 85-92 are connected through resistors 93-100 tooutputs of two flip-flops 101 and 102, together forming the counter 53.A reset output of flip-flop 101, on line 103 is connected to resistors93 and 99 and also to an input line of flip-flop 102. A set output offlip-flop 101 on line 104, is conected to resistors 94 and 96. A resetoutput of flip-flop 102, on line 105 is connected to resistors 97 and98. A set output of flip-flop 102, on line 106, is connected toresistors and 100. A set input of both flip-flops 101 and 102 isconnected through a line 108 to the output of the delay multivibrator56. A triggering input of flip-flop 101 is connected through a capacitor109 to the output of the delay multivibrator 54. Power supply terminalsfor both flip-flops 101 and 102 are connected to the junction betweentwo resistors 111 and 112, connected between ground and the power supplyterminal 45.

FIG. 4 graphically illustrates the operation of the circuitry of FIG. 3.The top four representations, numbered: l, 2", 3 and 4 indicate theintake, compression power and exhaust strokes for the engine cylinderscorresponding to injection valves 11-14. It is noted that these numbersdo not correspond directly to the conventional numbering of enginecylinders from front to rear. With an engine having a l,- 3, 4, 2 firingorder, the numbers 1, 2, 3 and 4 in FIG. 4 may respectively correspondto the numbers 3, 4, 2 and l cylinders, numbered from front to rear inthe engine.

Wave form 116 indicates the signal applied from the distributor 26through the line 57 to the input of delay multivibrator 56. This signalis in the form of an ignition pulse applied to the front cylinder,corresponding to the injection valve 13, being approximately coincidentwith the start of the power stroke of that cylinder which is the number3 cylinder using the designation of FIG. 4. Wave form 117 indicates thesignal developed at the output of the delay multivibrator 56 which isapplied through the line 108 to the set inputs of both flipflops 101 and102. The signal is in the form of a short pulse having a trailingnegative-going edge delayed by certain time interval after thetriggering pulse applied from the distributor. When the trailingnegative-going edge is applied to the set inputs of the flip-flops 101and 102, it insures that they will be placed in a set condition, if notalready in that condition.

Wave form 118 is that of the signal applied through line 55 to the delaymultivibrator 54 from the ignition coil 27, this signal being in theform of an ignition pulse developed at a time approximately coincidentwith the start of every power stroke.

Wave form 119 is that of the signal developed at the output of the delaymultivibrator 54 which is applied through the capacitor 109 to thetriggering signal input to the flip-flop 101. This signal was in theform of a series of pulses having negative-going trailing edges delayedby short time interval after the applied ignition pulses. Such trailingedges cause the flip-flop 101 to change its state from one state to theother.

Wave form 120 is that of the set output line 104 of the flip-flop 101which is caused to go high by the first illustrated pulse wave form 119,low" by the second, again high by the third, again low by the fourth andagain high by the fifth. It is noted that the trailing edge of the pulseof wave form 117 occurs after the trailing edge of the first illustratedpulse of wave form 119 and since flip-flop 101 is already in a setcondition, the pulses of wave form 117 have no effect. However, ifduring starting conditions, for example, the flip-flops 101 and 102 werenot in set conditions when the first pulse of wave form 117 is applied,the first pulse would then operate to inusre placing both flip-flops ina set condition at this point of the operation.

Wave form 121 is that of a signal at the reset output line 103 of theflip-flop 101 while wave forms 122 and 123 are of the signals at the setand reset output lines 106 and 105 of the flip-flop 102. It will benoted that the flip-flop 102 is shifted from one state to the other inresponse to negative-going portions of the signal applied thereto fromthe reset line 103 of the flip-flop 101, indicated by wave form 121.

Wave form 124 is that of the signal at the output of the flip-flop 51which is shifted low by the negativegoing trailing edges of the pulsesfrom delay multivibrator 54 (wave form 119) and which is shifted high bya signal applied from timer 3] through line 29, it being noted that theoperation of the timer 31 is initiated when the flip-flop 51 is shiftedlow, by a signal applied through line 30.

Wave forms 125-128 are those of the signals applied to the injectionvalves 11, 12, 13 and 14, which are in the form of positive pulsesduring the respective intake strokes of the cylinders with which valves11-14 are associated. It is noted that during the first 180 degrees ofengine rotation, the signals applied from the reset output lines 103 and105 of the flip-flops 101 and 102, wave forms 121 and 123, are low. Suchsignals are applied through the resistors 93 and 97 to the bases oftransistors and 89 which are cut off. The timing signal signal, waveform 124, is also low during part of the first 180 degrees of enginerotation and this signal is applied through the transistor 83, operativeas an emitterfollower, to the line 81 and from line 81 through theresistor 77 to the base of transistor 73, which is thus also cut off.With all three transistors 73, 85 and 89 cut off, the potential of thebase of the transistor 61 rises toward the potential of the power supplyterminal 45, being limited only by the flow of base-emitter currentthrough the resistor 69, and the driver transistor 61 conducts heavilythrough the injection valve 11, so long as the timing signal, wave form124, is low.

During the first l80 degrees of engine rotation, high signals areapplied to the bases of transistors 86, 87 and 88, and also 92, whichare rendered conductive to place the potentials of the bases of thedriver transistors 62, 63 and 64 at values close to ground potential.The driver transistors 62, 63 and 64 are thus nonconductive, and no cardis applied to the injection valves 12, 13 and 14.

During the next 180 degrees of engine rotation, the signals applied tothe bases of transistors 86 and 90 are both low, and the drivertransistor 62 is rendered conductive for the duration of the timingsignal from flipfiop 51 (wave form 124). At this time, the inputs totransistors 85, 87 and 88 are high preventing conduction of thetransistors 61, 63 and 64.

in a similar fashion, the driver transistors 63 and 64 are renderedconductive during the third and fourth 180 degree intervals of enginerotation, for time intervals equal to the duration of the timing signalfrom flipflop 51. It is noted that the wave forms 125-128, asillustrated, are rectangular pulses but in actual operation, the waveforms are distorted due to the inductance of the solenoid actuators anddue to inertial effects. Because of such inductance and inertialeffects,

the actual opening of the injection valve is delayed to take place afterthe leading edge of the applied pulse and likewise, the actual closingof the valve may be delayed. However, the actual time of opening of eachin- 60 jection valve and thereby the amountof fuel injectedareproportional to the duration of the timing pulse, to within closelimits of accuracy.

It is also noted that each injection valve may be opened throughoutnearly degrees of crankshaft rotation which is important in that therequired instantaneous rate of flow through each injection valve ornozzle, during the time it is opened, under maximum total flow ofconditions, is reduced since the valve is open for a longer timeinterval. The requirements as to design and construction of the valveare not nearly as stringent as they would be if the valve had to beopened for short periods of time with a correspondingly higher requiredinstantaneous rate of flow. Also, variations in opening and closingtimes of the valves, as well as varia tions in the accuracy ofgeneration of the timing signals, have a reduced effect on overallaccuracy. By way of example, the system may be designed for a 6millisecond maximum pulse length, for operation and up to 5,000 RPM.

It is noted that FIG. 2 illustrates the functional operations performed,whereas FIG. 3 illustrates the implementation of such functions in anactual circuit. in FIG. 2, the function of the decoder 52, illustratedin block form, is to produce a number of outputs in sequence, the numberbeing equal to the number of engine cylinders, and the function of theillustrated AND gates 47-50 is to combine such outputs of the decoder 52with the output of the timing flip-flop 51. In the actual circuit ofFIG. 3, these functions are implemented by using three input NOR gatesfor each of the driver transistors 61-64. For example, transistors 73,85 and 89 and associated circuit elements form a three input NOR gatefor the driver transistor 61, requiring three low inputs to produce ahigh output at the base of driver transistor 61. In a strict sense,there is no AND gate as such as that there is no individual circuit inwhich all inputs must have the same value to make the output equal toany of the inputs. However, in a broader sense, the functionaloperations are nevertheless performed, in that the transistors 85 and 89perform a decoding function, allowing the collectors thereof to gotoward high only when the flip-flops 101 and 102 are in prescribedstates, and through the common connection of the collectors oftransistors 85, 89 with the collector of the transistor 73, an ANDfunction is performed in that the decoding function must be performedandthe timing flip-flop 51 must be in a certain state in order to make theoutput have a certain value. It will be understood that other types oflogic circuit elements might be used to implement the prescribedfunctionsand that reference herein to AND and OR gates is intended in afunctional sense and not as limiting the invention to particularcircuits for implementation of the prescribed functions.

Referring now to FIG. 5, reference numeral 130 generally designatesanother preferred type of system, designed for use with an eightcylinder engine. As shown, eight injection valves 131-138 are connectedbetween a voltage supply terminal 140 and output terminals of eightdriver stages 141-148 having additional terminals connected to ground.Two timing flip-flops 149 and 150 are provided, an output of theflip-flop 149 being connected to inputs of one group of four AND gates151, 153, 155 and 157 and an output of the flip-flop 150 being connectedto inputs of a second group of four AND gates 152, 154, 156 and 158, theoutputs of the AND Gates 151-158 being respectively connected to inputsof the driver stages 141-148.

Additional inputs of the AND gates 151-158 are connected to outputs ofeight OR gates 161-168 having inputs connected to lines 171-178 whichare connected to outputs of an octal decoder 179, which is connected toathree bit counter 180. As shown, the inputs of OR I gate 161 areconnected to lines 171 and 172, the inputs of OR gate 163 are connectedto lines 173 and 174, the

inputs of OR gate 165 are connected to lines and 176, and the inputs ofOR gate 167 are connected to lines 177 and 178. Similarly, the inputs ofOR gate 162 are connected to lines 172 and 173, the inputs of OR gate 1are connected to lines 174 and 175, the inputs of OR gate 166 areconnected to lines 176 and 177 and the inputs of OR gate 168 areconnected to lines 178 and 171. The three bit counter 180 is connectedthrough lines 181 and 182 to an exitation and conditioning circuit 183controlled from an engine firing sensor 184. The exitation andconditioning circuit 183 may include delay monostable multivibratorssimilar to the multivibrators 54 and 56 of the circuit of FIG. 2 whilethe engine firing sensor 184 may include connections to a distributorand ignition coil of the engine, as described above in connection withFIGS. 1 and 2. It will be understood, however, that other forms ofcircuits may be employed for applying synchronizing signals to the threebit counter 180.

The flip-flops 149 and 150 have set inputs connected to lines 185 and186, line 185 being connected through four diodes 187 to the lines 171,173, 175 and 177 and the line 186 being connected through four diodes188 to lines 172, 174, 176 and 178. The diodes 187 and the diodes 188form two OR gates, applying triggering signals to the flip-flops 149 and150 in response to prescribed changes in state of the signals on thelines 171-178. Such triggering signals are also applied to an A timer189 and a B timer 190 which after controlled time intervals, apply resetsignals to the flip-flops 149 and 150. Timers 189 and 190 are connectedto a line 191 which may be connected to a computer operative in the samemanner as the computer 32, described above in connection with FIG. 1.

FIG. 6 illustrates the operation of the system 130 of FIG. 5. The topeight diagrams are of the intake, compression, power and exhaust strokesof the eight cylinders of the engine. numbered 1 through 8 andrespectively corresponding to the injection valves 131-138. Thenumbering of the representations corresponds to the order of firing andnot to the position of the engine cylinders. With an engine having a l,8, 4, 3, 6, 5, 7, 2 firing order, the numbers 1-8 in FIG. 6 may respectively correspond to cylinder locations 6, 5, 7, 2, 1, 8, 4 and 3.

Wave forms 201-208 are of the signals on lines 171-178, respectively,these signals being progressively or sequentially low during onecomplete cycle, corresponding to two turns of the engine crankshaft,each of the signals being low for 90 degrees of crankshaft rotation.

Wave forms 211-218 are of the signals at the outputs of the OR gate161-168, each of such signals being low during two consecutive lowsignals on the lines 171-178, and being thus low for 180 degrees ofcrankshaft rotation.

Wave forms 219 and 220 are of the signals at the outputs of theflip-flops 149 and 1511, applied to the AND gates 151, 153, 155 and 157and the AND gates 152, 154, 156 and 158. When any one of the lines 171,173, 175 or 177 goes low, a signal is applied through one of the diodes187 to the flip-flop 149 to cause the output thereof to go low and atthe same time, the operation of the A timer 189 is initiated from thesame signal, applied from line 185. After a certain time interval,determined by the voltage applied on line 191, the A timer 189 applies areset signal to the flip-flop 149 causing the output thereof to again gohigh. Similarly, the flipflop 150 is triggered to a set condition whenanyone of the signals on lines 172, 174, 176 or 178 goes low and isreset after a certain time interval by a signal applied from the B timer180.

Wave forms 221-228 are of the signals at the outputs of the AND gates151-158. It will be-noted that the signal at the output of the AND gate151 is low when both the signal applied from OR gate 161 (wave form 211)and the signal at the output of the flip-flop 149 (wave form 219) arelow. Similarly, thesignal at the output of I the AND gate 152 (wave form222) is low when both the output of the OR gate 162 (wave form 212) andthe output of the flip-flop 150 (wave form 220) are low. It will benoted that through the division of the circuitry into two groups andthrough the use of the two flipflops 149 and two timers 189 and 190, theoutput signalscan overlap. Thus, the end of the low portion of thesignal applied to the driver 141 can occur after the beginning of thelow portion of the signal applied to driver 142. The driver circuits,described hereinafter in connection with FIG. 10, are arranged toenergize the respective injection valves when the inputs thereof arelow. The reset signal applied to each of the flip-flops 149 and 150 fromthe respective timer 189 or 190 may occur at any point fromsubstantially less than 90 degrees of crankshaft rotation to nearly 180degrees, following the triggering of the flip-flop to its set conditionand thus the injection of fuel into each cylinder of the engine mayoccur throughout corresponding time intervals.

Referring now to FIG. 7, reference numeral 230 generally designatesanother type of system according to the invention designed for an eightcylinder engine. The system 230 is similar to the system 130 of FIG. 5,incorporating the eight injection valves 131-138, drivers 141-148,flip-flops 149 and 150, AND gates 151-158, OR gaes 161-168, octaldecoder 179, three bit counter 180, exitation and conditioning circuit183, engine firing sensors 184 and diodes 187 and 188, connected in thesame manner as shown in FIG. and as described above.

In the circuit 230, reset inputs of flip-flops 149 and 150 are connectedto outputs of a pair of AND gates 231 and 232 having inputs connected toreset and set outputs of a flip-flop 234, which has set and reset inputsconnected to the outputs of a pair of gates 235 and 236 having inputsconnected to the lines 185 and 186. A and B timers 237 and 238 areprovided which are operated sequentially, the A timer 237 beingtriggered by a signal from the exitation and conditioning circuit 183each time that a delayed ignition pulse or clock signal is applied fromthe exitation and conditioning circuit 183 to the three bit counter 180.The B timer 238 is triggered from the A timer 237 when the A timer 237times out. The output of the timer 237 is connected to inputs of thegates 235 and 236 while the output of timer 238 is connected to inputsof both AND gates 231 and 232.

The operation of the system 230 is similar to that of the system 130 ofFIG. 5 with respect to the generation of the wave forms 201-208 and211-218, illustrated in FIG. 6. The differences in operation areillustrated by wave forms in the upper part of FIG. 9. Referringthereto, wave form 241 is that of the signal at the output of the Atimer 237 which goes high in response to signals applied from theexitation and conditioning circuit 183, approximately coincident witheach clock signal applied to the counter 180 to change the statethereof. The output of timer 237 remains high for a controllable timeinterval controlled by a signal from a computer, applied on line 240.When the output of the timer 237 goes low it triggers the B timer 238 sothat the output of timer 238 goes high and also, through one or theother of the gates 235 or 236, the flip-flop 234 is triggered from onestate to the other. When the signal on any one of the lines 171, 173,175 or 177 is low, the negative-going part of the output signal of timer237 triggers the flip-flop 234 to a set condition. Similarly, when thesignal on any one of the lines 172, 174, 176 or 178 is low, thenegative-going portion of the signal output of the timer 237 triggersthe flip-flop 234 to a reset condition. After a controllable length oftime following triggering of the timer 238, the output signal thereofgoes low, wave form 242 being that of the output of the timer 238.

Wave forms 243 and 244 are those of the outputs of flip-flops 149 and150 while wave form 246 is that of the set output of flip-flop 234 whichis applied to the V gate 232. The reset output of flip-flop 234 is ofopposite phase and is applied to the gate 231.

In the operation as detected, flip-flop 149 is triggered each time thatany one of the signals on lines 171, 173, 175 or 177 goes low. It istriggered to a set condition in which the output thereof, shown by waveform 243 is low and it remains low until the output of the counter 238goes low while at the same time the reset output of the flip-flop 234 islow. Thus, the output of flip-flop 149 is low for a time interval equalto the time interval of operation of the timer 237 plus the timeinterval of operation of the timer 238. In a similar fashion, theflipflop 150 is triggered each time that any one of the signals on thelines 172, 174, 176 or 178 goes low and the output of flip-flop 150remains in a low condition until the output of the B timer 238 goes lowwhile at the same time, the flip-flop 234 is in a set condition. Thus,the flip-flop 150 remains in a set condition, with its output low for atime interval equal to the sum of the time intervals of operation of thetimers 237 and 238. Accordingly, the time intervals of operation of theflipflops 149 and 150 may overlap as illustrated. This will be the casewhen the output signals, applied to the injection valves, are to havedurations of greater than degrees of crankshaft rotation. The circuitryoperates in the same manner, however, when the output signals, appliedto the injection valves, have a duration of less than 90 degrees ofcrankshaft rotation.

Wave forms 251-258 are those of the signals applied to the driver stages141-148 with the circuit of FIG. 7. Wave form 251, for example,represents a combination of the wave form 243 at the output of theflip-flop 149 with the wave form 211 (FIG. 6) at the output of the ORgate 161.

Referring to FIG. 8, reference numeral 260 generally designates anothertype of system designed for an eight cylinder engine. This system issimilar in many respects to the system of FIG. 5 and the system 230 ofFIG. 7, incorporating injection valves 131-138, driver circuits 141-148,flip-flops 149 and 150, gates 151-158, gates 161-168, an octal decoder179, a counter 180, an exitation and conditioning circuit 183 and anengine firing sensor 184, operative in generally the same manner as thesame circuits shown in FIG. 5. It also incorporates gates 231 and 232, aflip-flop 234, gates 235 and 246 and timers 237 and 238 operative in thesame manner as described above in connection with FIG. 7. It is herenoted that the system of FIG. 8 could altematively utilize alternatelyoperating timers such as the timers 189 and 190 of FIG. 5.

The system 260 differs from the previously described systems in thatelectronic switches 261 and 262 are provided, switch 261 being connectedbetween the power supply terminal 140 and the upper terminals ofinjection valves 131, 133, 135 and 137 while switch 262 is connectedbetween the power supply terminal 140 and the upper terminals ofinjection valves 132,

134, 136 and 138. Switches 261 and 262 are operated by monostable stablemultivibrators 263 and 264, controlled from the flip-flops 149 and 150.In operation,

. the switch 261 is closed by the monostable multivibrator 263 during ashort initial portion of each output signal from the flip-flop 149 andsince one of the driver stages 141, 143, 145 or 147 is then operative,full operating current is applied to one of the injection valves 131,133, 135 or 137. After a short time interval, however, switch 261 isopened but thereafter current continues to flow through resistance meanswithin the switch 261 to maintain the operative injection valve openinguntil the flip-flop 149 is reset. The continued current flow is referredto herein as the post bias current and is substantially less than thefull operating current required to drive the injection valve to an opencondition, while being sufficient to maintain the injection valve open.With this feature, the change in current flow required to close thevalve is reduced, and the time of closing is more rapid and moreaccurately controlled.

Another feature of the system 260 is in the application of a pre-biascurrent to the injection valves, ahead of the opening times thereof. Inaccordance with this feature, eight diodes 271-278 are provided forapplying signals to the driver stages 141-148 during 90 degree timeintervals in advance of the respective opening times of the injectionvalves. Diodes 271-278 are respectively connected between the inputs ofdriver stages 141-148 and the lines 178 and 171-177.

The operation of the system of FIG. 8 is shown in the lower portion ofFIG. 9. Wave forms 281-288 are those of the signals applied to theinputs of the driver stages 141-148 in the system of FIG. 8,representing combinations of the signals developed at the outputs of thegates 151-158 (wave forms 251-258 in FIG. 9) and the signals on thelines 178 and 171-177 (wave forms 208 and 201-207, respectively, FIG.6).

Wave forms 291-298 represent the current flow through the respectiveinjection valves 131-138, using the system of FIG. 8. During the initialportion of the signal applied to the driver 141, for example, thecurrent flow is limited to a comparativley small value by resistancemeans within the switch 261, and the current, referred to as thepre-bias current is insufficient to open the injection valve 131.However, when the switch 261 is closed for a short time interval, alarge operating current is applied to the injection valve 131 to drivethe valve fully open. The current thereafter continues to flow throughthe injection valve 131, through the resistance means of the switch 261,and this postbias current, although equal to the pre-bias current, issufficient to keep the valve open since once the valve is open, thecurrent required to keep it open is smaller than that required toinitially drive it to an open condition. Each valve is kept open for atime interval dependent upon the control signal applied to the timers.

FIG. 10 illustrates the circuit of the driver stage 141, it beingunderstood that the other driver stages 142-148 may have the samecircuit. The signal input to the driver stage 141 is applied to the baseof a transistor 300, the base being also connected through a resistor301 to a power supply terminal 302 which may be at plus five voltsrelative to ground, for example. The emitter of transistor 300 isconnected to ground while the connector thereof is connected through aresistor 303 to a power supply terminal 304 which may be at plus 12 to14 volts relative to ground. The collector of transistor 300 is alsoconnected to the base of a power transistor 305, the emitter of which isconnected to ground and the collector of which is connected to outputterminal 306, connected to the injection valve 131.

FIG. 11 shows the circuits of the switch 261 and the monostablemultivibrator 263, it being understood that the switch 262 andmonostable multivibrator 264 may have the same circuits. An outputterminal 307, connected to terminals of the valves 131, 133, and 137 isconnected to the collector of a transistor 308, the emitter of which isconnected to a power supply terminal 309 which may be at plus 12 to 14volts relative to ground, for example. A resistor 310 is connected inparallel with the transistor 308, between terminals 307 and 309. Theresistor 310 has a value such as to maintain the proper pre and postbias currents. The base of transistor 308 is connected through aresistor 311 to the terminal 309 and is also connected through aresistor 312 to the collector of a transistor 313 the emitter of whichis grounded and the base of which is connected through a resistor 314 toa circuit point 315 which forms the output terminal of the monostablemultivibrator 263. Circuit point 315 is connected through a resistor 316to a power supply terminal 317 which may be at plus 10 volts relative toground, for example. Circuit point 315 is also connected to thecollector of a transistor 318 the emitter of which is grounded and thebase of which is connected through a fixed resistor 319 and anadjustable resistor 320 to the terminal 317. The base of transistor 318is also connected through a capacitor 321 to the collector of atransistor 322, the collector being also connected through a resistor323 to a power supply terminal 324 which may be at plus five voltsrelative to ground. The emitter of the transistor 322 is grounded whilethe base thereof is connected through a resistor 325 to the circuitpoint 315 and also through a capacitor 326 to the output of theflip-flop 149.

In operation, the transistor 318 is normally conducting and thecollector thereof being at a low potential, the base of the transistor313 is also at a low potential, preventing conduction thereof and alsopreventing conduction of the transistor 308. When a positivegoing signalis applied through the capacitor 326 to the base of the transistor 322,the transistor 322 conducts and the transistor 318 is cut off throughthe signal applied through capacitor 321 from the collector of thetransistor 322. With transistor 318 cut off, the transistor 313 isrendered conductive and the transistor 308 is also rendered conductiveto present virtually a short circuit between the terminals 307 and 308,thus permitting full operating current to be applied to the injectionvalve. After a certain time interval, the charge of 13 the capacitor 321is changed through current flow through the resistors 319 and 320 topennit the transistor 318 to conduct whereupon the transistor 322 is cutoff and likewise transistors 313 and 308 are cut off. The time ofoperation of the multivibrator 263 is adjustable by adjustment of theresistor 320.

What is claimed is:

1. A fuel injection control system for an engine including at least onegroup of four cylinders and fuel injection valve means associated witheach cylinder for injection of fuel for flow into each cylinder duringthe intake stroke thereof, and electrically energizable actuator meansfor each of said fuel injection valve means, said control systemcomprising sequencing means for supplying sequencing signals insynchronized relation to the intake strokes of the engine and furthercomprising for each group of four cylinders: four driver stagesrespectively coupled to the four actuator means of said group, each ofsaid four driver stages including transistor means arranged tocontrollably conduct current through the associated actuator means, fourAND gate means having outputs respectively coupled to said four driverstages, flip-flop means triggered to a first state at approximately thebeginnings of the intake strokes of said four cylinders and to a secondstate at controlled times varying from substantially less than 90degrees to substantially greater than 90 degrees following thebeginnings of the intake strokes of said four cylinders, means couplingsaid flip-flop means to inputs of all of said four gate means to apply aseries of four timing signals thereto during each 720 degrees of enginerotation, and means responsive to sequencing signals from saidsequencing means to supply four control signals to additional inputs ofsaid four gate means, each of said four control signals having aduration of approximately 180 degrees of engine rotation and beinggenerally coextensive with the intake stroke of one of said fourcylinders, said control system being arranged for control of an eightcylinder engine having two groups of four cylinders, and said flip-flopmeans for said two groups being operative to develop first and secondseries of timing signals in 90 degree phase displaced relation.

2. In a system as defined in claim 1, means for applying control signalsfrom said sequencing means to said flip-flop means to trigger saidflipflop means to said first stage thereof.

3. In a system as defined in claim 1, said sequencing means comprising aplurality of flip-flops forming a digital counter and arranged to counta predetermined number of pulses equal to the number of cylinders, anddecoder gate means coupled to said flip-flops.

4. In a system as defined in claim 3, means for applying triggeringpulses both to said flip-flop means for determining the starting timesof said timing signals and to said counter to advance the count thereof.

5. In a system as defined in claim 1, wherein said engine is an eightcylinder engine having two groups of four cylinders, said flip-flopmeans for said two groups being operative to develop first and secondseries of timing signals in 90 degree phase displaced relation.

6. In a system as defined in claim 1, said sequencing means beingoperativeto develop eight control signals in sequence during theprogressive firing of all eight cylinders and eight OR gates eachresponsive to consecutive control signals for applying signals to saidadditional inputs of said AND gate means.

7. In a system as defined in claim 1, said sequencing means beingoperative to develop control signals in sequence during the progressivefiring of all eight cylinders, first OR gate means for setting the firstflip-flop means associated with one group of four cylinders in responseto alternate ones of said control signals from said sequencing means,and second OR gate means for setting the flip-flop means for the othergroup of four engine cylinders in response to the remaining ones of saidcontrol signals from said sequencing means.

8. In a system as defined in claim 1, first and second timers forcontrolling the triggering to said second state of said flip-flop meansfor the two groups of cylinders.

9. In a system as defined in claim 8, said first and second timers beingconnected in cascade, a third flip-flop operated in synchronizedrelation to said first and second series of timing signals, and meanscontrolled by said third flip-flop for alternately controlling saidfirst and second flip-flops from said second timer.

10. In a system as defined in claim 9, means applying signals from saidfirst timer to said third flip-flop to alternately change said thirdflip-flop from one state to the other.

11. A fuel injection control system for an engine including a pluralityof cylinders and fuel injection valve means associated with eachcylinder for injection of fuel for flow into each cylinder during theintake stroke thereof, and electrically energizable actuator means foreach of said fuel injection valve means, said control system comprising:a driver stage for each of said actuator means, said driver stageincluding transistors means arranged to controllably conduct currentthrough said actuator means, means associated with said driver stagesfor initially applying a pre-bias current to each of said actuator meansand subsequently applying a larger operating current thereto, saidpre-bias current being insufficient to cause opening of the associatedvalve means while being sufficient to allow rapid opening thereof inresponse to said larger operating current, and said pre-bias currentbeing applied for a substantial time interval in advance of applicationof said larger operating current to pre-condition said actuator meansfor rapid opening in response to application of said larger operatingcurrent.

12. In a system as defined in claim 11, means associated with saiddriver stages for applying after application of said larger operatingcurrent a smaller post-bias current sufficient to maintain theassociated valve means in an open condition while being small enough 14.A fuel injection control system for an engine including a plurality ofcylinders and fuel injection valve means associated with each cylinderfor injection of fuel for flow into each cylinder during the intakestroke thereof, and electrically energizable actuator means for each ofsaid fuel injection valve means, said control system comprising: adriver stage for each of said actuator means, each driver stageincluding transistor means arranged to controllably conduct currentthrough said actuator means, power supply means having first and secondterminals, said transistor means including a first transistor associatedwith a plurality of said driver stages for connection of said firstpower supply tenninal to one terminal of a plurality of said actuatormeans, and a plurality of additional transistors respectively associatedwith said plurality of driver stages for connecting the other terminalsof said plurality of said actuator means to said second power supplyterminal, means for applying timing signals to said plurality ofadditional transistors for conduction thereof, means oper ative duringeach timing signal for rendering said first transistor highly conductivefor a short time interval, and resistance means connected in parallelrelation to said first transistor.

15. In a system as defined in claim 14, each of said additionaltransistors being rendered conductive for a substantial time interval inadvance of said short time interval of conduction of said firsttransistor, said resistance means having a value such as to establish aprebias current insufficient to cause opening of the associated valvemeans while being sufficient to allow rapid opening thereof in responseto conduction of said first transistor.

16. In a system as defined in claim 15, each of said additionaltransistors being also conductive for a substantial time intervalfollowing said short time interval, said resistance means having a valuesuch as to establish a post-bias current sufficient to maintain theassociated valve means in an open condition while being small enough forrapid closing thereof in response to termination of conduction of theassociated one of said additional transistors.

17. In a system as defined in claim 14, each of said additionaltransistors being conductive for a substantial time interval followingsaid short time interval, said resistance means having a value such asto establish a post-bias current sufficient to maintainthe associatedvalve means in an open condition while being small enough for rapidclosing thereof in response to termination of conduction of theassociated one of said additional transistors.

